What is a board foot, and how is it calculated?

A board foot is 144 cubic inches of lumber: a piece 1 inch thick, 12 inches wide and 1 foot long. Because length is in feet and the other two sides are in inches, the sum is thickness times width times length times quantity, divided by twelve. One 2 x 6 at 8 feet is 2 x 6 x 8 / 12, which is 8.00 board feet, and six boards of 1 in by 7 1/4 in by 8 ft come to 29.00 board feet.

What is the difference between nominal and actual dimensions?

Nominal is a named size; actual is the dimension you measure. Common dry surfaced softwood examples in this table include nominal 1 x 8 at 3/4 x 7 1/4 and nominal 2 x 4 at 1 1/2 x 3 1/2. These are comparisons, not measurements of your boards or a universal supplier billing rule. Six nominal 1 x 8 boards at 8 feet give 32.00 board feet using the entered dimensions and 21.75 using the common surfaced comparison. Nominal mode keeps those figures separate and labels a partial comparison when some sizes are absent from the table. Confirm actual measurements and which dimensions are used in your supplier quote.

What do 4/4 and 8/4 mean on a hardwood rack?

They are thicknesses counted in quarter inches, which is how rough hardwood is graded and priced. 4/4 is four quarters, or 1.00 in; 5/4 is 1.25 in; 8/4 is 2.00 in. Type them straight into the thickness field, with the slash, and the calculator reads them as inches. A plain decimal works too, so 1.5 and 6/4 are the same board.

How do I cost a whole pile of lumber?

Add a row for each rectangular size, using quantity for boards that share dimensions, then enter your own price per board foot. Each row volume is rounded half up to two decimals; its cost is that rounded volume times the complete supplied rate, rounded to cents. Those row costs are added. A supplied rate of 2.675 remains 2.675 in the report. No currency, supplier rate, taxes, species or grade is inferred. This calculates cost from a supplied rate; it does not solve a rate from a supplied total cost.

Is length entered in feet or inches?

Length is entered in feet, while thickness and width are in inches. That mix is not an oversight, it is the definition: dividing by twelve converts the one foot of length into the twelve inches that make the 144 cubic inches of a board foot. A board 30 inches long is 2.5 feet, so type 2.5.

Do the printed rows add up to the printed total?

Yes. Every row volume rounds half up to two decimals, then those rounded rows are added. Two rows of exactly 11/3 board feet each therefore print 3.67 + 3.67 = 7.34, rather than 7.33 from rounding the exact combined volume. Each row cost also rounds to cents before adding. A positive row below 0.005 board feet prints 0.00 under this policy; the report keeps its complete exact physical volume. Invalid rows are refused with a message naming the row.

Board Foot Calculator

Calculate board feet the standard way: thickness in inches times width in inches times length in feet times quantity, divided by twelve. A board foot is 144 cubic inches of lumber, so a single 2 x 6 at 8 feet is 8.00 board feet. What it does differently is take a row per board instead of one size at a time, so a whole order totals in one place, and keep the two dimension conventions apart and labelled. The same six 1 x 8 boards at 8 feet bill at 32.00 board feet as nominal sizes and hold 21.75 board feet of wood once surfaced to 3/4 x 7 1/4, and the tool shows you which convention it just used. Thickness takes the rack notation, so 4/4 is 1.00 in, 5/4 is 1.25 in and 8/4 is 2.00 in. Add a price per board foot to cost the pile, then print or copy the cut list. The nominal and surfaced figures above describe this table example, not a billing rule or a guarantee of delivered dimensions. The entered-size total rounds each row half up to two decimals before adding; the complete report also gives the exact volume before row rounding. Cost uses the complete supplied rate and rounds each row cost to cents before adding. This page handles supplied rectangular boards; log or standing-tree yield, live-edge outlines, weight and inverse area or linear conversions need other workflows.

Total board feet29.00bf1 rows · 6 boardsEntered actual dimensions, as measured. Confirm the dimensions used in your quote.

The total counts the fields above plus every row in the list, so one board never needs adding. Add row (or Enter) moves it to the list and clears the fields for the next size. Thickness takes the rack notation: 4/4 is 1.00 in, 5/4 is 1.25 in and 8/4 is 2.00 in. Every row is rounded to two decimals and the total is the sum of those rows, so the printed lines add up to the printed total.

The cut list

The complete report used for the print dialog and native clipboard: a line per size, the convention those sizes were entered in, and the totals.

Board foot cut list
Entered actual dimensions, as measured. Confirm the dimensions used in your quote.
Policy: each row volume rounds half up to two decimals, then rows are added. Cost uses each rounded row volume times the complete supplied rate, rounded to cents per row, then added.
1. Supplied 1 in x 7.25 in x 8 ft, 6 boards: 29.00 bf
   Exact dimensions: 1 in x 7.25 in x 8 ft; quantity 6; physical volume 29 bf (exact 29).
Total: 29.00 board feet from 6 boards
Full physical volume before row rounding: 29 bf (exact 29).
A displayed 0.00 row can have positive physical volume below 0.005 bf. Large shortened values use an ellipsis; this report retains all input and exact values.
Rectangular supplied boards only. Log/tree yield, live-edge shape, weight, inverse area/linear conversions and insulation coverage are not calculated.

1 rows, 6 boards, 29.00 board feet.

Complete selectable report

Board foot cut list
Entered actual dimensions, as measured. Confirm the dimensions used in your quote.
Policy: each row volume rounds half up to two decimals, then rows are added. Cost uses each rounded row volume times the complete supplied rate, rounded to cents per row, then added.
1. Supplied 1 in x 7.25 in x 8 ft, 6 boards: 29.00 bf
   Exact dimensions: 1 in x 7.25 in x 8 ft; quantity 6; physical volume 29 bf (exact 29).
Total: 29.00 board feet from 6 boards
Full physical volume before row rounding: 29 bf (exact 29).
A displayed 0.00 row can have positive physical volume below 0.005 bf. Large shortened values use an ellipsis; this report retains all input and exact values.
Rectangular supplied boards only. Log/tree yield, live-edge shape, weight, inverse area/linear conversions and insulation coverage are not calculated.

Nominal sizes and what they measure

Common dry surfaced softwood comparisons. Nominal mode calculates the entered dimensions and separately applies this illustrative table. Actual mode uses your measurements. These comparisons do not establish the dimensions of supplied material or the sizes used in a quote; measure the boards and confirm those terms. Hardwood is different again: it is usually sold by quarter thickness, so 4/4 and 8/4 go in the thickness field as 1.00 and 2.00.

Sold as	Measures	8 ft, entered size	8 ft, table size
1 × 2 in	3/4 × 1 1/2 in	1.33	0.75
1 × 3 in	3/4 × 2 1/2 in	2.00	1.25
1 × 4 in	3/4 × 3 1/2 in	2.67	1.75
1 × 6 in	3/4 × 5 1/2 in	4.00	2.75
1 × 8 in	3/4 × 7 1/4 in	5.33	3.63
1 × 10 in	3/4 × 9 1/4 in	6.67	4.63
1 × 12 in	3/4 × 11 1/4 in	8.00	5.63
5/4 × 4 in	1 × 3 1/2 in	3.33	2.33
5/4 × 6 in	1 × 5 1/2 in	5.00	3.67
2 × 2 in	1 1/2 × 1 1/2 in	2.67	1.50
2 × 3 in	1 1/2 × 2 1/2 in	4.00	2.50
2 × 4 in	1 1/2 × 3 1/2 in	5.33	3.50
2 × 6 in	1 1/2 × 5 1/2 in	8.00	5.50
2 × 8 in	1 1/2 × 7 1/4 in	10.67	7.25
2 × 10 in	1 1/2 × 9 1/4 in	13.33	9.25
2 × 12 in	1 1/2 × 11 1/4 in	16.00	11.25
4 × 4 in	3 1/2 × 3 1/2 in	10.67	8.17
4 × 6 in	3 1/2 × 5 1/2 in	16.00	12.83

Exact arithmetic, and the convention stated. Exact arithmetic on the numbers you enter: thickness in inches times width in inches times length in feet times quantity, divided by twelve. What it cannot know is which dimensions your supplier bills on, so nominal and actual are kept separate here and the one in use is shown beside the total. A nominal 1 × 8 at 8 feet, six boards, gives 32.00 board feet from the entered sizes and 21.75 from the common surfaced comparison. Neither chooses the dimensions on a supplier invoice. Price per board foot is your figure, in your currency, and it is multiplied rather than looked up.

Common questions

What is a board foot, and how is it calculated?: A board foot is 144 cubic inches of lumber: a piece 1 inch thick, 12 inches wide and 1 foot long. Because length is in feet and the other two sides are in inches, the sum is thickness times width times length times quantity, divided by twelve. One 2 x 6 at 8 feet is 2 x 6 x 8 / 12, which is 8.00 board feet, and six boards of 1 in by 7 1/4 in by 8 ft come to 29.00 board feet.
What is the difference between nominal and actual dimensions?: Nominal is a named size; actual is the dimension you measure. Common dry surfaced softwood examples in this table include nominal 1 x 8 at 3/4 x 7 1/4 and nominal 2 x 4 at 1 1/2 x 3 1/2. These are comparisons, not measurements of your boards or a universal supplier billing rule. Six nominal 1 x 8 boards at 8 feet give 32.00 board feet using the entered dimensions and 21.75 using the common surfaced comparison. Nominal mode keeps those figures separate and labels a partial comparison when some sizes are absent from the table. Confirm actual measurements and which dimensions are used in your supplier quote.
What do 4/4 and 8/4 mean on a hardwood rack?: They are thicknesses counted in quarter inches, which is how rough hardwood is graded and priced. 4/4 is four quarters, or 1.00 in; 5/4 is 1.25 in; 8/4 is 2.00 in. Type them straight into the thickness field, with the slash, and the calculator reads them as inches. A plain decimal works too, so 1.5 and 6/4 are the same board.
How do I cost a whole pile of lumber?: Add a row for each rectangular size, using quantity for boards that share dimensions, then enter your own price per board foot. Each row volume is rounded half up to two decimals; its cost is that rounded volume times the complete supplied rate, rounded to cents. Those row costs are added. A supplied rate of 2.675 remains 2.675 in the report. No currency, supplier rate, taxes, species or grade is inferred. This calculates cost from a supplied rate; it does not solve a rate from a supplied total cost.
Is length entered in feet or inches?: Length is entered in feet, while thickness and width are in inches. That mix is not an oversight, it is the definition: dividing by twelve converts the one foot of length into the twelve inches that make the 144 cubic inches of a board foot. A board 30 inches long is 2.5 feet, so type 2.5.
Do the printed rows add up to the printed total?: Yes. Every row volume rounds half up to two decimals, then those rounded rows are added. Two rows of exactly 11/3 board feet each therefore print 3.67 + 3.67 = 7.34, rather than 7.33 from rounding the exact combined volume. Each row cost also rounds to cents before adding. A positive row below 0.005 board feet prints 0.00 under this policy; the report keeps its complete exact physical volume. Invalid rows are refused with a message naming the row.

Exact arithmetic on the numbers you enter: thickness in inches times width in inches times length in feet times quantity, divided by twelve. What it cannot know is which dimensions your supplier bills on, so nominal and actual are kept separate here and the one in use is shown beside the total.